Colon cancer affects over 100,000 people per year, according to statistics from the American Cancer Society. Over 40,000 additional new cases of rectal cancer are diagnosed annually. Combined, the two cancers form a group called colorectal cancers.

Like all cancers, the causes are known only incompletely. Many begin as benign clumps of cells called polyps, which resemble small mushrooms in the intestine. Some of them go on to develop into carcinomas. Healthy cells become misshapen and reproduce too rapidly until they form tumors.

In many affected individuals symptoms may be non-existent for quite some time. When they do develop, they're frequently in the form of changes in bowel movements, such as constipation or diarrhea. That may be accompanied by abdominal pain, or the pain may occur by itself. Persistent gas or cramps are another sign.

Over time, symptoms may worsen to include rectal bleeding (often a side-effect of straining during periods of constipation, but may result from lesions) and bloody stool. Unexplained weight loss can occur, as well as excessive fatigue. Of course, since any of these symptoms can occur with dozens, even hundreds, of other diseases and conditions, only a professional diagnosis can determine whether they're due to colorectal cancer.

Like most cancers, risk factors are diverse and numerous. Increasing age ups the odds of nearly every form. More than 90% of colon cancers are diagnosed in persons over 50. Certain diseases or conditions, like Crohn's or colitis, increase the odds of secondary medical problems like colon cancer. Genetics plays a role, with some families more prone to cancer than others. Having diabetes increases the odds of developing colon cancer.

But there are also a great many controllable risk factors.

Diet can affect your chances of developing colon cancer. High fat, low fiber diets are strongly correlated with increased odds of cancer of many types, including colorectal. Whether eating red meat and processed meats increases the odds is still a very uncertain and controversial position and research is ongoing on the subject.

What is known is that individuals in Western Europe and the U.S. are more likely to develop them and the effect is strongly correlated with diet. Exactly what aspect of that diet is the culprit is still unknown, though.

Related to both diet and exercise, obesity ups the odds of colon cancer, as it does with a whole range of diseases. The odds of the cancer being fatal also rise with increasing levels of obesity. High alcohol consumption is both related to that statistic and an independent risk factor, as is heavy smoking.

Fortunately, there are many thorough and relatively low discomfort screening tests for colon cancer. A stool blood test is completely painless, since it's non-invasive. A colonoscopy may be mildly uncomfortable to some individuals. A barium enema, followed by an X-ray regime can detect polyps or cancerous tumors over a certain size.

Like any cancer, early detection and treatment is both the least painful and offers the best prognosis. See your physician to examine your options.